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The Effect of Harvest Moisture and Bale Wrapping on Forage Quality, Temperature, and Mold in Orchardgrass Hay
Journal of Equine Veterinary Science 31 (2011) 711-716
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Original Research
The Effect of Harvest Moisture and Bale Wrapping on Forage Quality, Temperature, and Mold in Orchardgrass Hay Krishona Martinson PhD a , Wayne Coblentz PhD b, Craig Sheaffer PhD c a
Department of Animal Science, University of Minnesota, St. Paul, MN Research Dairy Scientist, USDA-ARS US Dairy Forage Research Center, Marshfield, WI c Department of Agronomy and Plant Genetics, University of Minnesota, St Paul, MN b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 13 February 2011 Received in revised form 07 April 2011 Accepted 02 May 2011 Available online 03 August 2011
Effects of harvest moisture and bale wrapping on forage quality and mold formation in orchardgrass (Dactylis glomerata L.) hay have not been investigated. The objectives of this study were to determine the effects of initial bale moisture and plastic wrapping on temperature, forage quality (protein, fiber components, and digestible energy), and mold formation in large round-baled orchardgrass hay. In all, 40 round bales of mature orchardgrass hay measuring 1.2 1.5 m2 were baled at three different moisture ranges (eight bales per treatment): 124 to 166 g/kg (low moisture); 180 to 232 g/kg (intermediate moisture); and 259 to 337 g/kg (high moisture). Selected bales within each moisture range were individually wrapped in plastic (16 bales), and temperature sensors were placed in each bale for up to 10 weeks. The lowest (P .01) maximum temperature and heating degree-day accumulations were observed when initial bale moisture content was 124 g/kg or when hay was wrapped, regardless of initial moisture content. In 2008 and 2009, all wrapped hays resulted in similar forage quality (P .14) and mold counts (P ¼ .94) compared with 124 g/kg moisture hay. Hay baled at 166 g/kg resulted in fiber (P .82) and mold (P ¼ .21) components similar to higher moisture bales. Mold counts for hay baled at 166 g/kg and 124 g/kg moisture were 24.8 106 and 2.7 104 CFU/g, respectively, demonstrating that large round bales are prone to molding at relatively low moisture concentrations. Maintenance of forage quality and reduction in mold growth were achieved by baling dry (124 g/kg moisture) or wrapping round bales of orchardgrass hay up to 337 g/kg moisture. Ó 2011 Elsevier Inc. All rights reserved.
Keywords: Bale wrapping Forage quality Heating degree-days Mold Orchardgrass
1. Introduction Harvesting hay can be complicated by poor drying conditions (i.e., high humidity and heavy dew) and the threat of rainfall [1]. In an effort to avoid rain and other adverse weather conditions, hay is often baled before adequate drying to recommended moisture levels, resulting in mold development and reduced forage quality [2-6]. Corresponding author at: Krishona Martinson, PhD, Department of Animal Science, University of Minnesota, 1364 Eckles Avenue, St. Paul, MN 55108. E-mail address: [email protected] (K. Martinson). 0737-0806/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jevs.2011.05.003
Recommended moisture at time of baling is dependent on several factors, including bale size. The upper threshold moisture at baling for storage of small square bales (approximately 45 kg) is about 200 g/kg, whereas the threshold for larger hay bales is assumed to be lower [7]. Hays baled at moisture levels of <150 g/kg are assumed to be relatively stable and typically exhibit little evidence of microbial respiration [5]. However, this has not been investigated thoroughly for cool-season grass hays or large round bales intended for equine feeding. Hay that is baled at a moisture content above recommended levels commonly undergoes spontaneous heating in which plant sugars are respired into carbon dioxide, water, and heat [5]. Spontaneous heating can result from prolonged plant
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respiration as well as mold growth [4,6]. In addition to dust and mycotoxins associated with excessive mold growth, heating can result in significant dry matter losses and deleterious changes in forage nutritive value [2-4]. The development of mold in baled hay has been correlated to increased moisture at baling [4]. It is common knowledge that horses are highly sensitive to several molds, and that ingesting moldy feed can result in both short-term and long-term respiratory problems, specifically heaves, and gastrointestinal problems like colic [8]. In Sweden, researchers investigated wrapping individual round bales of grass hay, primarily timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis L.), in plastic at approximately 350 g/kg moisture [9]. Wrapping bales at this moisture level resulted in minimal fermentation, and the resulting forage was offered to equines without causing adverse health effects. Bale wrapping has not been researched extensively for equine use in the United States, but may be a strategy to aid in producing high-quality horse hay. The objectives of this research were to determine the effects of initial bale moisture and plastic wrapping on internal bale temperatures, forage quality (protein, fiber components, and digestible energy [DE]), and mold formation in large round bales of orchardgrass hay.
2. Materials and Methods Over a 2-year period (2008 and 2009), 40 (1.2 1.5 m2) round bales (16 in 2008; 24 in 2009) were baled and tied with three revolutions of net wrap (Deere and Co., Moline, IL) from a 15-hectare field located near Albertville, Minnesota (45 20 N, 90 60 W). All forage was the initial growth harvested from a pure stand of orchardgrass, variety unknown, ranging from full flower to the anthesis stage of growth. Targeted moisture ranges included low moisture (LM), <150 g/kg; intermediate moisture (IM), 180 to 250 g/kg; and high moisture (HM), 300 to 350 g/kg. Moisture at time of baling was estimated with a forage moisture probe (model F-2,000, Delmhorst, Towaco, NJ) and later confirmed through oven drying of a subsample. In 2008, optimum drying conditions allowed baling of hay throughout the same day, beginning with HM and ending with LM bales. To obtain different moisture ranges in 2009, HM and IM bales were baled throughout the first day, whereas LM bales were baled the next day. For each harvest, forage was mowed and conditioned with a Discbine (model 730, Deere and Co.,), raked with a high capacity 12-wheel wheel rake (H&S Manufacturing and Co. Inc., Marshfield, WI), and then baled with a round baler (model 457, Deere and Co.). The bales were stored outside on a well-drained sod surface in one continuous row running east and west. Bales within a treatment group were butted tightly against each other, and nontreatment bales were placed between treatment groups and on both ends of the row. Each year, the treatments were applied in a completely randomized design with four replications. In 2008, treatments included LM, IM, HM, and HM wrapped with plastic (HMW). In 2009, plastic wrapping was added to all moisture treatments, resulting in six baling treatments
(LM and LM wrapped [LMW], IM and IM wrapped [IMW], and HM and HMW). Immediately after baling, each bale was cored (2 51 cm2) six times, and samples were analyzed for forage quality by a commercial forage testing laboratory (DHIA Laboratories, Sauk Centre, MN). Forage quality components included moisture content, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), equine DE, calcium (Ca), and phosphorus (P). Samples were ground, dried at 105 C for 3 hours, and weighed to determine dry matter percentage. Concentrations of CP, ADF, and NDF were determined in accordance with the Association of Official Agricultural Chemists [10] protocols (methods 990.02, 973.18, and 2002.04, respectively). Equine DE was calculated using an equation developed by Pagen [11], and Ca and P were analyzed in accordance with the Environmental Protection Agency method 3040B [12]. After sampling, three temperature data loggers (model HOBO UA-001-08, Onset, Bourne, MA) were placed in each bale about 61 cm from either flat end of the bale at depths of 38, 72, and 114 cm from the top of the bale. After the temperature sensors were placed, the HMW bales in 2008 and the LMW, IMW, and HMW bales in 2009 were immediately wrapped six times with one mil plastic wrap with a bale wrapper (model 780, Anderson Group Co., Chesterville, Quebec, Canada). Temperature sensors recorded temperature every hour for 7 (2008) or 10 (2009) weeks. Heating degree-days (HDD) were computed as the summations of the daily increment by which the average internal bale temperature was greater than 30 C [12]. After the temperature sensors were removed, six additional cores were taken from each bale to determine forage quality, mold counts, and mold identification. Forage quality analysis was conducted as previously described. Mold counts and identifications were determined through pour plate methodology using potato dextrose agar (2008) or dichloran rose bengal chloramphenicol agar (2009) and peptone buffer (2008) or Butterfield’s phosphate buffer (2009) diluent. A total of 50 g of test material was diluted with 45 mL of peptone buffer in 2008 and 5 g of test material was diluted with 45 mL of Butterfield’s phosphate buffer in 2009. Serial dilutions were made to yield four dilutions, which were plated with peptone buffer with tetracycline hydrochloride as an antibiotic (2008) or 101 to 106 dilutions, which were plated with tempered dichloran rose bengal chloramphenicol agar (2009). Plates were incubated in an upright position at 25 C to 27 C for 5 to 7 days. Identification of mold genus was based on colony morphology. Data were analyzed as a completely randomized design using PROC GLM of SAS (SAS Institute Inc., 2003, SAS software 9.1, Cary, NC). Individual bales constituted the experimental unit. During both 2008 and 2009, there were four replications (bales) for all baling treatments. Because of the expanded treatment structure during 2009, data from each year were analyzed independently. To compare treatment responses, a series of orthogonal contrasts was developed for each production year. For 2008, contrasts included (i) unwrapped hays with elevated moisture concentrations (IM, HM) versus the LM control; (ii) IM versus HM; and (iii) all wrapped bales (HMW) versus the LM control. For 2009, contrasts included (i) IM and HM
K. Martinson et al. / Journal of Equine Veterinary Science 31 (2011) 711-716
versus the LM control; (ii) IM versus HM; (iii) all wrapped hays (LMW, IMW, and HMW) versus the LM control; (iv) IMW and HMW versus LMW; and (v) IMW versus HMW. Significance was declared at the P < .05 level of confidence, and relevant tendencies were noted at P < .10. 3. Results 3.1. Moisture Content and Temperature Characteristics Initial bale moisture differed (P < .01) among treatments in 2008. However, the LM treatment was slightly greater (166 g/kg) than the target moisture range of <150 g/kg, whereas IM and HM treatments were within or near initial moisture targets (Table 1). Compared with LM, the maximum temperature was greater for IM and HM (P < .01), and lower for HMW (P ¼ .04). The maximum temperature also differed (P < .01) between IM and HM, with HM having the greatest maximum temperature (77 C). Similar trends among treatments were observed for HDD accumulation. When compared with LM controls, IM and HM had greater (P < .01) HDD accumulations. However, IM and HM also differed from each other (P ¼ .01), with HM accumulating 1,281 HDD (Table 1). Wrapping (HMW) greatly reduced (P ¼ .09) accumulation of HDD, relative to LM controls (7 vs. 209 HDD) and the unwrapped HM bale. Wrapping HM bales also greatly reduced maximum temperature (32 C vs.77 C, respectively) and HDD accumulation (7 vs. 1,281, respectively) as compared with the unwrapped MW bales (standard error of the mean [SEM]: 4 and 80, respectively). Initial bale moisture was different (P < .01) among treatments in 2009. However, the HMW treatment was slightly less (259 g/kg) than the target moisture range of 300 to 350 g/kg, whereas all other treatments were within initial moisture targets (Table 2). When compared with LM, the maximum temperature was greater for IM and HM (P < .01), but there was no difference (P ¼ .60) between LM and all wrapped hays, regardless of their initial bale moisture. Maximum temperature also differed (P < .01)
Table 1 Initial moisture concentrations and heating characteristics for orchardgrass hays made during 2008 Treatment Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped HM wrapped (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM HMW vs. LM
HDDa >30 C
Initial Bale Moisture (g/kg)
Maximum Temperature ( C)
166 232
45 60
209 932
298
77
1,281
337
32
7
9
4
80
<0.01 <0.01 <0.01
<0.01 <0.01 0.04
<0.01 0.01 0.09
LM, low moisture; IM, intermediate moisture; HM, high moisture; HMW, high moisture wrapped. a Heating degree-days (HDD) is the summations of the daily increment by which the average internal bale temperature was greater than 30 C.
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Table 2 Initial moisture concentrations and heating characteristics for orchardgrass hays made during 2009 Treatments Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped Control (LMW) Intermediate (IMW) High (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM LMW, IMW, HMW vs. LM IMW, HMW vs. LMW IMW vs. HMW.
HDDa >30 C
Initial Bale Moisture (g/kg)
Maximum Temperature ( C)
124 213
46 63
47 640
334
82
1,216
123
49
100
180
50
155
259 14
43 2
86 103
<0.01 <0.01 <0.01
<0.01 <0.01 0.60
<0.01 <0.01 0.58
<0.01
0.45
0.87
<0.01
0.04
0.64
LMW, low moisture wrapped; IMW, intermediate moisture wrapped. a Heating degree-days (HDD) is the summations of the daily increment by which the average internal bale temperature was greater than 30 C.
between IM and HM, with HM exhibiting the greatest maximum temperature of any baling treatment (82 C). Similar relationships among treatments were observed for HDD accumulation. When compared with LM, IM and HM exhibited greater (P < .01) HDD accumulations, with HM accumulating the greatest HDD of any treatment (1,216 HDD). There was no difference (P ¼ .58) between HDD accumulations or maximum temperatures for the LM control as compared with all wrapped hay treatments. 3.2. Forage Quality and Mold In both 2008 and 2009, initial (prestorage) treatments exhibited no meaningful differences across forage quality components, and were therefore grouped into common prestorage mean values for each year (n ¼ 16 in 2008; n ¼ 24 in 2009). No treatment differences (P .08) were observed for CP in 2008 (Table 3). Although the unwrapped hays differed in moisture content, maximum temperature, and HDD, they had similar NDF, ADF, equine DE, and mold counts. Wrapping (HMW) lowered (P < .01) NDF and ADF and increased (P < .04) DE as compared with LM controls. Differences (P ¼.05) were measured between IM and HM for concentrations of Ca, and between LM and HMW (P ¼ .04) for concentrations of P. The wrapped treatment (HMW) had lower (P ¼ .04) mold count as compared with LM. Aspergillus mold species were found in all treatments, Cladosporium was found in all unwrapped treatments, and Fusarium was found in the LM treatment. In 2009, hay CP concentration was similar for all the unwrapped treatments. Concentrations of NDF and ADF increased with increasing initial bale moisture concentration in unwrapped hays (P < .01), but equine DE decreased (Table 4). A contrasting trend was observed for wrapped
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Table 3 Forage quality characteristics for orchardgrass hays baled during 2008 Treatment
CP (g/kg)
NDF (g/kg)
ADF (g/kg)
Ca (g/kg)
P (g/kg)
Equine DE (Mcal/kg)
Mold (CFU/g)
Initial SEM Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped High (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM HMW vs. LM
76 1.5
636 4
402 2.5
33 0.15
28 0.03
2.00 0.013
e e
74 76 81
658 664 655
424 424 420
30 24 33
31 31 32
1.94 1.98 1.96
24.8 106 19.7 106 5.5 106
82 3
626 7
395 4.5
28 0.29
34 0.09
2.05 0.029
8.6 104 7.5 106
0.73 0.05 0.72
0.66 0.26 0.04
0.60 0.52 0.04
0.22 0.24 0.08
0.87 0.34 <0.01
0.82 0.53 <0.01
0.21 0.20 0.04
CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; Ca, calcium; P, phosphorous; equine DE, equine digestible energy.
hays, with greater (P < .04) concentrations of fiber components in LMW as compared with IMW and HMW. IMW and HMW hays had a lower (P ¼ .04) CP concentration as compared with LMW (Table 4). Wrapped hay (LMW, IM, HMW) had similar ADF and NDF as the LM control but had greater (P < .01) equine DE as compared with LM. Hay Ca and P concentrations did not differ (P .19) among treatments. Mold counts were greater (P < .01) for IM and HM than for LM control. Wrapped treatments did not differ (P ¼ .94) from LM controls with respect to mold counts and had lower mold counts than the unwrapped IM and HM treatments. Aspergillus mold species were found in all treatments except LM, and Fusarium was found in the LM, IMW, and HMW treatments. 4. Discussion Our results agree with previous research that determined alfalfa (Medicago sativa L.), and mixed grass-legume hays baled at moisture concentrations of <150 g/kg are relatively stable in terms of mold growth and forage quality [5,13]. Orchardgrass hay baled at 124 g/kg had low mold counts and lower HDD accumulations as compared with unwrapped bales harvested at higher moisture levels (213 to 334 g/kg). In contrast, large round bales of mixed alfalfa-orchardgrass
hay were prone to spontaneous heating when initial concentrations of bale moisture were >160 g/kg [13], and our results agree with those from this study. When we baled orchardgrass at 166 g/kg moisture HDD accumulations, mold counts and deleterious effects on forage quality were similar to hay baled at 232 or 298 g/kg moisture. On the basis of these findings, we conclude that orchardgrass packaged in large round bales is susceptible to molding and forage quality losses at relatively LM concentrations. Orchardgrass hay baled at greater (166g/kg) moisture concentrations had reduced forage quality, mainly resulting from increases in fiber components (NDF and ADF) and mold counts (Table 4). Increased concentrations of fiber components in higher moisture hays have been reported for other forage species [3,14]. Increased concentrations of NDF and ADF were observed in bermudagrass (Cynodon dactylon L.) hay baled at 219 to 302 g/kg moisture [15] and alfalfa-orchardgrass round bales baled at 230 g/kg moisture [13]. Changes in fiber components are thought to occur primarily by indirect mechanisms, where the respiratory activity of microorganisms has a concentrating effect on fiber constituents by preferentially oxidizing nonfiber components [5]. These deleterious changes in forage quality also affected livestock utilization negatively when heat-damaged bermudagrass was offered to steers [16].
Table 4 Forage quality characteristics for orchardgrass hays baled during 2009 Treatment
CP (g/kg)
NDF (g/kg)
ADF (g/kg)
Ca (g/kg)
P (g/kg)
Initial SEM Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped Control (LMW) Intermediate (IMW) High (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM LMW, IMW, HMW vs. LM IMW, HMW vs. LMW IMW vs. HMW
102 3.5
592 3
365 3
46 0.20
27 0.05
2.03 0.013
e e
93 79 90
582 607 664
358 360 427
47 45 43
28 25 28
2.05 2.05 1.83
2.6 104 7.1 106 5.3 106
97 74 83 6.5
582 558 553 10
364 346 350 6
44 47 52 0.37
28 27 28 0.13
2.07 2.20 2.20 0.033
5.1 1.9 2.6 9.9
0.45 0.64 0.94 0.25 0.43
0.29 0.19 0.59 0.76 0.43
0.29 0.25 0.28 0.04 0.33
<0.01 <0.01 0.14 0.04 0.71
<0.01 <0.01 0.47 0.04 0.57
Equine DE (Mcal/kg)
0.01 <0.01 0.01 0.01 0.91
Mold (CFU/g)
<0.01 0.22 0.94 0.94 0.87
104 104 105 105
K. Martinson et al. / Journal of Equine Veterinary Science 31 (2011) 711-716
Coblentz and Hoffman [17] determined that moisture concentration of hay at the time of baling positively influenced subsequent heat development during storage. In our study, initial moisture contents of 298 and 334 g/kg resulted in the greatest accumulation of HDD (1,281 and 1,216, respectively). Wrapping bales resulted in similar HDD accumulations as compared with hay baled at 124 g/kg moisture, and the HDD accumulation of wrapped bales was not affected by initial bale moisture. High mold counts in IM, HM, and LM bales during 2008 are likely related to generally greater initial concentrations of bale moisture as compared with 2009. Greater HDD accumulations in wetter, unwrapped bales were a result of microbial activity, and mold growth has previously been associated with spontaneous heating of hay bales during storage [5,18]. Adams et al. [19] evaluated the mold development and associated mycotoxins in livestock feedstuffs and reported the following conclusions: (i) <500,000 CFU/g of mold is considered safe to feed to livestock; (ii) 500,000 to 1 million CFU/g is relatively safe; (iii) >1 million CFU/g should be fed with caution; and (iv) any feedstuff with >5 million CFU/g should not be fed. Using these recommendations, all wrapped forage and LM in 2009 (124 g/kg moisture) would be considered desirable equine forage. All other treatments resulted in mold counts that were 5 million CFU/g and are not appropriate equine feeds. Aspergillus species of mold were found in every treatment except LM in 2009, and Fusarium was found in four treatments. Aspergillus and Fusarium species are commonly found in insufficiently dried hay [6,20-22] and can lead to production of mycotoxins [8,21,22]. In 2008, wrapping of HM (337 g/kg) hay resulted in lower fiber components, greater equine DE, and lower mold counts than hay baled at 166 to 298 g/kg. In 2009, wrapping orchardgrass round-bales made at 123 to 259 g/kg resulted in similar forage quality and mold counts as compared with hay baled at 124 g/kg of initial moisture. Previous research has demonstrated that wrapped orchardgrass round-bales at moisture concentrations of 456 g/kg were relatively stable after unwrapping for as long as 32 days during the winter [23]. In Sweden, hay wrapped at 350 g/kg moisture was fed to equines without causing adverse health effects in them [9]. 5. Conclusions Maintenance of forage quality and reduction in mold growth were achieved by baling dry (124 g/kg) hay or wrapping, regardless of initial moisture, round-bales of orchardgrass hay. Therefore, the currently recommended moisture threshold of 150 g/kg [5] for safe storage of alfalfa or mixed hays is appropriate for orchardgrass as well. This recommendation should be carefully followed; orchardgrass bales were prone to significant molding and forage quality losses at moisture concentrations (i.e., 166 g/kg) slightly greater than 150 g/kg. This abrupt line between high-quality and damaged, moldy hay likely is one reason why some horse owners assume that it is difficult to harvest and feed quality round-bales to horses. Wrapping higher-moisture orchardgrass round-bales is an effective method for maintaining forage quality. However, the
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stability of higher moisture bales after unwrapping, especially during the summer months or with intermittent feeding schedules, needs further investigation. Acknowledgments The authors thank the assistance of Beth Allen, Grace Dahlgren, Kris Moncada, and the cooperation of Leaning Pine Farm and McNamara Farm Services. This research was funded by a grant from Midwest Forage Association with additional support from Kemin Industries, Inc. and Cropland Genetics. References [1] Moser LE. Post-harvest physiology changes in forage plants. In: Moore KJ, Peterson MA, editors. Post-harvest physiology and preservation of forages. Madison, WI: ASA, CSSA; 1995. p. 1-20. CSSA Special Publication 22. [2] Coblentz WK, Fritz JO, Bolsen KK, Cochran RC. Quality changes in alfalfa hay during storage in bales. J Dairy Sci 1996;79:873-85. [3] Coblentz WK, Turner JE, Scarbrough DA, Lesmeister KE, Johnson ZB, Kellogg DW, et al. Storage characteristics and quality changes in bermudagrass hay as affected by moisture content and density of rectangular bales. Crop Sci 2000;40:1375-83. [4] Roberts CA. Microbiology of stored forages. In: Moore KJ, Peterson MA, editors. Post-harvest physiology and preservation of forages. Madison, WI: ASA, CSSA; 1995. p. 21. CSSA Special Publication 22. [5] Rotz CA, Muck RE. Changes in forage quality during harvest and storage. In: Proceeding of the National Conference on Forage Quality, Evaluation, and Utilization, Lincoln, NE. Madison, WI: ASA, CSSA, SSSA; 1994. p. 828-68. [6] Scudamore KA, Livesey CT. Occurrence and significance of mycotoxins in forage crops and silage: a review. J Food Sci Food Agric 1998;77:1-17. [7] Collins M, Paulson WH, Finner MF, Jorgensen NA, Keuler CR. Moisture and storage effects on dry matter and quality losses of alfalfa in round bales. Trans ASAE 1987;30:913-7. [8] Smith TK, Girish CK. The effects of feed born mycotoxins on equine performance and metabolism. In: Mycotoxins in Farm Animals. Kerala, India: Transworld Research Network; 2008. p. 48-70. [9] Muhonen S, Julliand V, Lindberg JE, Bertilsson J, Jansson A. Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay. J Anim Sci 2009;87:2291-8. [10] AOAC. Official methods of analysis. 17th ed. Arlington, VA: Association of Official Analytical Chemists; 2000. [11] Pagan JD. Measuring the digestible energy content of horse feeds. In: Advances in equine nutrition. Nottingham, UK: Nottingham University Press; 1998. p. 71-6. [12] EPA. Method 3050B. 1996. Available at: http://www.caslab.com/ EPA-Method-3050B/. [13] Montgomery MJ, Tineo A, Bledsoe BL, Baxter HD. Effect of moisture content at baling on nutritive value of alfalfa orchardgrass hay in conventional and large round bales. J Dairy Sci 1986;69:1847-53. [14] Goering HK, Gordon CH, Hemken RW, Waldo DR, Van Soest PJ, Smith LW. Analytical estimates of nitrogen digestibility in heat damaged forages. J Dairy Sci 1972;55:1275-80. [15] Turner JE, Coblentz WK, Scarbrough DA, Coffey KP, Kellogg DW, McBeth LJ, et al. Changes in nutritive value of bermudagrass hay during storage. Agron J 2002;94:109-17. [16] McBeth LJ, Coffey KP, Coblentz WK, Hellwig DH, Turner JE, Scarbrough DA. Impact of heating-degree-day accumulation during storage of bermudagrass hay on in situ degradation kinetics from steers. Anim Feed Sci Technol 2003;108:147-58. [17] Coblentz WK, Hoffman PC. Effects of bale moisture and bale diameter on spontaneous heating, dry matter recovery, in-vitro true digestibility, and in-situ disappearance kinetics of alfalfaorchardgrass hays. J Dairy Sci 2009;92:2853-74. [18] Roberts CA, Moore KJ, Graffis DW, Kirby HW, Walgenbach RP. Chitin as an estimate of mold in hay. Crop Sci 1987;27:783-5. [19] Adams RS, Kephart KB, Ishler VA, Hutchinson LJ, Roth GW. Mold and mycotoxin problems in livestock feeding. University Park, PA: The Pennsylvania State University, College of Agricultural Sciences and Cooperative Extension Publication; 1993. p. 16. DAS 93-21.
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[20] Clevstroem G, Goransson B, Hodverson R, Pettersson H. Aflatoxin formation in hay treated with formic acid and in isolated strains of Aspergillus flavus. J Stored Prod Res 1981;17:151-61. [21] Raymond SL, Smith TK, Swamy HV. Effects of feeding a blend of grains naturally contaminated with Fusarium mycotoxins on feed intake, serum chemistry, and hematology of horses, and the efficacy of a polymeric glucomannan mycotoxin adsorbent. J Anim Sci 2003;81:2123-30.
[22] Raymond SL, Heiskanen M, Smith TK, Reiman M, Laitinen S, Clarke AF. An investigation of the concentrations of selected fusarium mycotoxins and the degree of mold contamination of fielddried hay. J Equine Vet Sci 2000;20:616-21. [23] Rhein RT, Coblentz WK, Turner JE, Rosenkrans CF, Jr, Ogden RK, Kellogg DW. Aerobic stability of wheat and orchardgrass round-bale silages during winter. J Dairy Sci 2005;88: 1815-26.
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Original Research
The Effect of Harvest Moisture and Bale Wrapping on Forage Quality, Temperature, and Mold in Orchardgrass Hay Krishona Martinson PhD a , Wayne Coblentz PhD b, Craig Sheaffer PhD c a
Department of Animal Science, University of Minnesota, St. Paul, MN Research Dairy Scientist, USDA-ARS US Dairy Forage Research Center, Marshfield, WI c Department of Agronomy and Plant Genetics, University of Minnesota, St Paul, MN b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 13 February 2011 Received in revised form 07 April 2011 Accepted 02 May 2011 Available online 03 August 2011
Effects of harvest moisture and bale wrapping on forage quality and mold formation in orchardgrass (Dactylis glomerata L.) hay have not been investigated. The objectives of this study were to determine the effects of initial bale moisture and plastic wrapping on temperature, forage quality (protein, fiber components, and digestible energy), and mold formation in large round-baled orchardgrass hay. In all, 40 round bales of mature orchardgrass hay measuring 1.2 1.5 m2 were baled at three different moisture ranges (eight bales per treatment): 124 to 166 g/kg (low moisture); 180 to 232 g/kg (intermediate moisture); and 259 to 337 g/kg (high moisture). Selected bales within each moisture range were individually wrapped in plastic (16 bales), and temperature sensors were placed in each bale for up to 10 weeks. The lowest (P .01) maximum temperature and heating degree-day accumulations were observed when initial bale moisture content was 124 g/kg or when hay was wrapped, regardless of initial moisture content. In 2008 and 2009, all wrapped hays resulted in similar forage quality (P .14) and mold counts (P ¼ .94) compared with 124 g/kg moisture hay. Hay baled at 166 g/kg resulted in fiber (P .82) and mold (P ¼ .21) components similar to higher moisture bales. Mold counts for hay baled at 166 g/kg and 124 g/kg moisture were 24.8 106 and 2.7 104 CFU/g, respectively, demonstrating that large round bales are prone to molding at relatively low moisture concentrations. Maintenance of forage quality and reduction in mold growth were achieved by baling dry (124 g/kg moisture) or wrapping round bales of orchardgrass hay up to 337 g/kg moisture. Ó 2011 Elsevier Inc. All rights reserved.
Keywords: Bale wrapping Forage quality Heating degree-days Mold Orchardgrass
1. Introduction Harvesting hay can be complicated by poor drying conditions (i.e., high humidity and heavy dew) and the threat of rainfall [1]. In an effort to avoid rain and other adverse weather conditions, hay is often baled before adequate drying to recommended moisture levels, resulting in mold development and reduced forage quality [2-6]. Corresponding author at: Krishona Martinson, PhD, Department of Animal Science, University of Minnesota, 1364 Eckles Avenue, St. Paul, MN 55108. E-mail address: [email protected] (K. Martinson). 0737-0806/$ - see front matter Ó 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jevs.2011.05.003
Recommended moisture at time of baling is dependent on several factors, including bale size. The upper threshold moisture at baling for storage of small square bales (approximately 45 kg) is about 200 g/kg, whereas the threshold for larger hay bales is assumed to be lower [7]. Hays baled at moisture levels of <150 g/kg are assumed to be relatively stable and typically exhibit little evidence of microbial respiration [5]. However, this has not been investigated thoroughly for cool-season grass hays or large round bales intended for equine feeding. Hay that is baled at a moisture content above recommended levels commonly undergoes spontaneous heating in which plant sugars are respired into carbon dioxide, water, and heat [5]. Spontaneous heating can result from prolonged plant
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respiration as well as mold growth [4,6]. In addition to dust and mycotoxins associated with excessive mold growth, heating can result in significant dry matter losses and deleterious changes in forage nutritive value [2-4]. The development of mold in baled hay has been correlated to increased moisture at baling [4]. It is common knowledge that horses are highly sensitive to several molds, and that ingesting moldy feed can result in both short-term and long-term respiratory problems, specifically heaves, and gastrointestinal problems like colic [8]. In Sweden, researchers investigated wrapping individual round bales of grass hay, primarily timothy (Phleum pratense L.) and meadow fescue (Festuca pratensis L.), in plastic at approximately 350 g/kg moisture [9]. Wrapping bales at this moisture level resulted in minimal fermentation, and the resulting forage was offered to equines without causing adverse health effects. Bale wrapping has not been researched extensively for equine use in the United States, but may be a strategy to aid in producing high-quality horse hay. The objectives of this research were to determine the effects of initial bale moisture and plastic wrapping on internal bale temperatures, forage quality (protein, fiber components, and digestible energy [DE]), and mold formation in large round bales of orchardgrass hay.
2. Materials and Methods Over a 2-year period (2008 and 2009), 40 (1.2 1.5 m2) round bales (16 in 2008; 24 in 2009) were baled and tied with three revolutions of net wrap (Deere and Co., Moline, IL) from a 15-hectare field located near Albertville, Minnesota (45 20 N, 90 60 W). All forage was the initial growth harvested from a pure stand of orchardgrass, variety unknown, ranging from full flower to the anthesis stage of growth. Targeted moisture ranges included low moisture (LM), <150 g/kg; intermediate moisture (IM), 180 to 250 g/kg; and high moisture (HM), 300 to 350 g/kg. Moisture at time of baling was estimated with a forage moisture probe (model F-2,000, Delmhorst, Towaco, NJ) and later confirmed through oven drying of a subsample. In 2008, optimum drying conditions allowed baling of hay throughout the same day, beginning with HM and ending with LM bales. To obtain different moisture ranges in 2009, HM and IM bales were baled throughout the first day, whereas LM bales were baled the next day. For each harvest, forage was mowed and conditioned with a Discbine (model 730, Deere and Co.,), raked with a high capacity 12-wheel wheel rake (H&S Manufacturing and Co. Inc., Marshfield, WI), and then baled with a round baler (model 457, Deere and Co.). The bales were stored outside on a well-drained sod surface in one continuous row running east and west. Bales within a treatment group were butted tightly against each other, and nontreatment bales were placed between treatment groups and on both ends of the row. Each year, the treatments were applied in a completely randomized design with four replications. In 2008, treatments included LM, IM, HM, and HM wrapped with plastic (HMW). In 2009, plastic wrapping was added to all moisture treatments, resulting in six baling treatments
(LM and LM wrapped [LMW], IM and IM wrapped [IMW], and HM and HMW). Immediately after baling, each bale was cored (2 51 cm2) six times, and samples were analyzed for forage quality by a commercial forage testing laboratory (DHIA Laboratories, Sauk Centre, MN). Forage quality components included moisture content, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), equine DE, calcium (Ca), and phosphorus (P). Samples were ground, dried at 105 C for 3 hours, and weighed to determine dry matter percentage. Concentrations of CP, ADF, and NDF were determined in accordance with the Association of Official Agricultural Chemists [10] protocols (methods 990.02, 973.18, and 2002.04, respectively). Equine DE was calculated using an equation developed by Pagen [11], and Ca and P were analyzed in accordance with the Environmental Protection Agency method 3040B [12]. After sampling, three temperature data loggers (model HOBO UA-001-08, Onset, Bourne, MA) were placed in each bale about 61 cm from either flat end of the bale at depths of 38, 72, and 114 cm from the top of the bale. After the temperature sensors were placed, the HMW bales in 2008 and the LMW, IMW, and HMW bales in 2009 were immediately wrapped six times with one mil plastic wrap with a bale wrapper (model 780, Anderson Group Co., Chesterville, Quebec, Canada). Temperature sensors recorded temperature every hour for 7 (2008) or 10 (2009) weeks. Heating degree-days (HDD) were computed as the summations of the daily increment by which the average internal bale temperature was greater than 30 C [12]. After the temperature sensors were removed, six additional cores were taken from each bale to determine forage quality, mold counts, and mold identification. Forage quality analysis was conducted as previously described. Mold counts and identifications were determined through pour plate methodology using potato dextrose agar (2008) or dichloran rose bengal chloramphenicol agar (2009) and peptone buffer (2008) or Butterfield’s phosphate buffer (2009) diluent. A total of 50 g of test material was diluted with 45 mL of peptone buffer in 2008 and 5 g of test material was diluted with 45 mL of Butterfield’s phosphate buffer in 2009. Serial dilutions were made to yield four dilutions, which were plated with peptone buffer with tetracycline hydrochloride as an antibiotic (2008) or 101 to 106 dilutions, which were plated with tempered dichloran rose bengal chloramphenicol agar (2009). Plates were incubated in an upright position at 25 C to 27 C for 5 to 7 days. Identification of mold genus was based on colony morphology. Data were analyzed as a completely randomized design using PROC GLM of SAS (SAS Institute Inc., 2003, SAS software 9.1, Cary, NC). Individual bales constituted the experimental unit. During both 2008 and 2009, there were four replications (bales) for all baling treatments. Because of the expanded treatment structure during 2009, data from each year were analyzed independently. To compare treatment responses, a series of orthogonal contrasts was developed for each production year. For 2008, contrasts included (i) unwrapped hays with elevated moisture concentrations (IM, HM) versus the LM control; (ii) IM versus HM; and (iii) all wrapped bales (HMW) versus the LM control. For 2009, contrasts included (i) IM and HM
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versus the LM control; (ii) IM versus HM; (iii) all wrapped hays (LMW, IMW, and HMW) versus the LM control; (iv) IMW and HMW versus LMW; and (v) IMW versus HMW. Significance was declared at the P < .05 level of confidence, and relevant tendencies were noted at P < .10. 3. Results 3.1. Moisture Content and Temperature Characteristics Initial bale moisture differed (P < .01) among treatments in 2008. However, the LM treatment was slightly greater (166 g/kg) than the target moisture range of <150 g/kg, whereas IM and HM treatments were within or near initial moisture targets (Table 1). Compared with LM, the maximum temperature was greater for IM and HM (P < .01), and lower for HMW (P ¼ .04). The maximum temperature also differed (P < .01) between IM and HM, with HM having the greatest maximum temperature (77 C). Similar trends among treatments were observed for HDD accumulation. When compared with LM controls, IM and HM had greater (P < .01) HDD accumulations. However, IM and HM also differed from each other (P ¼ .01), with HM accumulating 1,281 HDD (Table 1). Wrapping (HMW) greatly reduced (P ¼ .09) accumulation of HDD, relative to LM controls (7 vs. 209 HDD) and the unwrapped HM bale. Wrapping HM bales also greatly reduced maximum temperature (32 C vs.77 C, respectively) and HDD accumulation (7 vs. 1,281, respectively) as compared with the unwrapped MW bales (standard error of the mean [SEM]: 4 and 80, respectively). Initial bale moisture was different (P < .01) among treatments in 2009. However, the HMW treatment was slightly less (259 g/kg) than the target moisture range of 300 to 350 g/kg, whereas all other treatments were within initial moisture targets (Table 2). When compared with LM, the maximum temperature was greater for IM and HM (P < .01), but there was no difference (P ¼ .60) between LM and all wrapped hays, regardless of their initial bale moisture. Maximum temperature also differed (P < .01)
Table 1 Initial moisture concentrations and heating characteristics for orchardgrass hays made during 2008 Treatment Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped HM wrapped (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM HMW vs. LM
HDDa >30 C
Initial Bale Moisture (g/kg)
Maximum Temperature ( C)
166 232
45 60
209 932
298
77
1,281
337
32
7
9
4
80
<0.01 <0.01 <0.01
<0.01 <0.01 0.04
<0.01 0.01 0.09
LM, low moisture; IM, intermediate moisture; HM, high moisture; HMW, high moisture wrapped. a Heating degree-days (HDD) is the summations of the daily increment by which the average internal bale temperature was greater than 30 C.
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Table 2 Initial moisture concentrations and heating characteristics for orchardgrass hays made during 2009 Treatments Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped Control (LMW) Intermediate (IMW) High (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM LMW, IMW, HMW vs. LM IMW, HMW vs. LMW IMW vs. HMW.
HDDa >30 C
Initial Bale Moisture (g/kg)
Maximum Temperature ( C)
124 213
46 63
47 640
334
82
1,216
123
49
100
180
50
155
259 14
43 2
86 103
<0.01 <0.01 <0.01
<0.01 <0.01 0.60
<0.01 <0.01 0.58
<0.01
0.45
0.87
<0.01
0.04
0.64
LMW, low moisture wrapped; IMW, intermediate moisture wrapped. a Heating degree-days (HDD) is the summations of the daily increment by which the average internal bale temperature was greater than 30 C.
between IM and HM, with HM exhibiting the greatest maximum temperature of any baling treatment (82 C). Similar relationships among treatments were observed for HDD accumulation. When compared with LM, IM and HM exhibited greater (P < .01) HDD accumulations, with HM accumulating the greatest HDD of any treatment (1,216 HDD). There was no difference (P ¼ .58) between HDD accumulations or maximum temperatures for the LM control as compared with all wrapped hay treatments. 3.2. Forage Quality and Mold In both 2008 and 2009, initial (prestorage) treatments exhibited no meaningful differences across forage quality components, and were therefore grouped into common prestorage mean values for each year (n ¼ 16 in 2008; n ¼ 24 in 2009). No treatment differences (P .08) were observed for CP in 2008 (Table 3). Although the unwrapped hays differed in moisture content, maximum temperature, and HDD, they had similar NDF, ADF, equine DE, and mold counts. Wrapping (HMW) lowered (P < .01) NDF and ADF and increased (P < .04) DE as compared with LM controls. Differences (P ¼.05) were measured between IM and HM for concentrations of Ca, and between LM and HMW (P ¼ .04) for concentrations of P. The wrapped treatment (HMW) had lower (P ¼ .04) mold count as compared with LM. Aspergillus mold species were found in all treatments, Cladosporium was found in all unwrapped treatments, and Fusarium was found in the LM treatment. In 2009, hay CP concentration was similar for all the unwrapped treatments. Concentrations of NDF and ADF increased with increasing initial bale moisture concentration in unwrapped hays (P < .01), but equine DE decreased (Table 4). A contrasting trend was observed for wrapped
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Table 3 Forage quality characteristics for orchardgrass hays baled during 2008 Treatment
CP (g/kg)
NDF (g/kg)
ADF (g/kg)
Ca (g/kg)
P (g/kg)
Equine DE (Mcal/kg)
Mold (CFU/g)
Initial SEM Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped High (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM HMW vs. LM
76 1.5
636 4
402 2.5
33 0.15
28 0.03
2.00 0.013
e e
74 76 81
658 664 655
424 424 420
30 24 33
31 31 32
1.94 1.98 1.96
24.8 106 19.7 106 5.5 106
82 3
626 7
395 4.5
28 0.29
34 0.09
2.05 0.029
8.6 104 7.5 106
0.73 0.05 0.72
0.66 0.26 0.04
0.60 0.52 0.04
0.22 0.24 0.08
0.87 0.34 <0.01
0.82 0.53 <0.01
0.21 0.20 0.04
CP, crude protein; NDF, neutral detergent fiber; ADF, acid detergent fiber; Ca, calcium; P, phosphorous; equine DE, equine digestible energy.
hays, with greater (P < .04) concentrations of fiber components in LMW as compared with IMW and HMW. IMW and HMW hays had a lower (P ¼ .04) CP concentration as compared with LMW (Table 4). Wrapped hay (LMW, IM, HMW) had similar ADF and NDF as the LM control but had greater (P < .01) equine DE as compared with LM. Hay Ca and P concentrations did not differ (P .19) among treatments. Mold counts were greater (P < .01) for IM and HM than for LM control. Wrapped treatments did not differ (P ¼ .94) from LM controls with respect to mold counts and had lower mold counts than the unwrapped IM and HM treatments. Aspergillus mold species were found in all treatments except LM, and Fusarium was found in the LM, IMW, and HMW treatments. 4. Discussion Our results agree with previous research that determined alfalfa (Medicago sativa L.), and mixed grass-legume hays baled at moisture concentrations of <150 g/kg are relatively stable in terms of mold growth and forage quality [5,13]. Orchardgrass hay baled at 124 g/kg had low mold counts and lower HDD accumulations as compared with unwrapped bales harvested at higher moisture levels (213 to 334 g/kg). In contrast, large round bales of mixed alfalfa-orchardgrass
hay were prone to spontaneous heating when initial concentrations of bale moisture were >160 g/kg [13], and our results agree with those from this study. When we baled orchardgrass at 166 g/kg moisture HDD accumulations, mold counts and deleterious effects on forage quality were similar to hay baled at 232 or 298 g/kg moisture. On the basis of these findings, we conclude that orchardgrass packaged in large round bales is susceptible to molding and forage quality losses at relatively LM concentrations. Orchardgrass hay baled at greater (166g/kg) moisture concentrations had reduced forage quality, mainly resulting from increases in fiber components (NDF and ADF) and mold counts (Table 4). Increased concentrations of fiber components in higher moisture hays have been reported for other forage species [3,14]. Increased concentrations of NDF and ADF were observed in bermudagrass (Cynodon dactylon L.) hay baled at 219 to 302 g/kg moisture [15] and alfalfa-orchardgrass round bales baled at 230 g/kg moisture [13]. Changes in fiber components are thought to occur primarily by indirect mechanisms, where the respiratory activity of microorganisms has a concentrating effect on fiber constituents by preferentially oxidizing nonfiber components [5]. These deleterious changes in forage quality also affected livestock utilization negatively when heat-damaged bermudagrass was offered to steers [16].
Table 4 Forage quality characteristics for orchardgrass hays baled during 2009 Treatment
CP (g/kg)
NDF (g/kg)
ADF (g/kg)
Ca (g/kg)
P (g/kg)
Initial SEM Unwrapped Control (LM) Intermediate (IM) High (HM) Wrapped Control (LMW) Intermediate (IMW) High (HMW) SEM Contrasts IM, HM vs. LM IM vs. HM LMW, IMW, HMW vs. LM IMW, HMW vs. LMW IMW vs. HMW
102 3.5
592 3
365 3
46 0.20
27 0.05
2.03 0.013
e e
93 79 90
582 607 664
358 360 427
47 45 43
28 25 28
2.05 2.05 1.83
2.6 104 7.1 106 5.3 106
97 74 83 6.5
582 558 553 10
364 346 350 6
44 47 52 0.37
28 27 28 0.13
2.07 2.20 2.20 0.033
5.1 1.9 2.6 9.9
0.45 0.64 0.94 0.25 0.43
0.29 0.19 0.59 0.76 0.43
0.29 0.25 0.28 0.04 0.33
<0.01 <0.01 0.14 0.04 0.71
<0.01 <0.01 0.47 0.04 0.57
Equine DE (Mcal/kg)
0.01 <0.01 0.01 0.01 0.91
Mold (CFU/g)
<0.01 0.22 0.94 0.94 0.87
104 104 105 105
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Coblentz and Hoffman [17] determined that moisture concentration of hay at the time of baling positively influenced subsequent heat development during storage. In our study, initial moisture contents of 298 and 334 g/kg resulted in the greatest accumulation of HDD (1,281 and 1,216, respectively). Wrapping bales resulted in similar HDD accumulations as compared with hay baled at 124 g/kg moisture, and the HDD accumulation of wrapped bales was not affected by initial bale moisture. High mold counts in IM, HM, and LM bales during 2008 are likely related to generally greater initial concentrations of bale moisture as compared with 2009. Greater HDD accumulations in wetter, unwrapped bales were a result of microbial activity, and mold growth has previously been associated with spontaneous heating of hay bales during storage [5,18]. Adams et al. [19] evaluated the mold development and associated mycotoxins in livestock feedstuffs and reported the following conclusions: (i) <500,000 CFU/g of mold is considered safe to feed to livestock; (ii) 500,000 to 1 million CFU/g is relatively safe; (iii) >1 million CFU/g should be fed with caution; and (iv) any feedstuff with >5 million CFU/g should not be fed. Using these recommendations, all wrapped forage and LM in 2009 (124 g/kg moisture) would be considered desirable equine forage. All other treatments resulted in mold counts that were 5 million CFU/g and are not appropriate equine feeds. Aspergillus species of mold were found in every treatment except LM in 2009, and Fusarium was found in four treatments. Aspergillus and Fusarium species are commonly found in insufficiently dried hay [6,20-22] and can lead to production of mycotoxins [8,21,22]. In 2008, wrapping of HM (337 g/kg) hay resulted in lower fiber components, greater equine DE, and lower mold counts than hay baled at 166 to 298 g/kg. In 2009, wrapping orchardgrass round-bales made at 123 to 259 g/kg resulted in similar forage quality and mold counts as compared with hay baled at 124 g/kg of initial moisture. Previous research has demonstrated that wrapped orchardgrass round-bales at moisture concentrations of 456 g/kg were relatively stable after unwrapping for as long as 32 days during the winter [23]. In Sweden, hay wrapped at 350 g/kg moisture was fed to equines without causing adverse health effects in them [9]. 5. Conclusions Maintenance of forage quality and reduction in mold growth were achieved by baling dry (124 g/kg) hay or wrapping, regardless of initial moisture, round-bales of orchardgrass hay. Therefore, the currently recommended moisture threshold of 150 g/kg [5] for safe storage of alfalfa or mixed hays is appropriate for orchardgrass as well. This recommendation should be carefully followed; orchardgrass bales were prone to significant molding and forage quality losses at moisture concentrations (i.e., 166 g/kg) slightly greater than 150 g/kg. This abrupt line between high-quality and damaged, moldy hay likely is one reason why some horse owners assume that it is difficult to harvest and feed quality round-bales to horses. Wrapping higher-moisture orchardgrass round-bales is an effective method for maintaining forage quality. However, the
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stability of higher moisture bales after unwrapping, especially during the summer months or with intermittent feeding schedules, needs further investigation. Acknowledgments The authors thank the assistance of Beth Allen, Grace Dahlgren, Kris Moncada, and the cooperation of Leaning Pine Farm and McNamara Farm Services. This research was funded by a grant from Midwest Forage Association with additional support from Kemin Industries, Inc. and Cropland Genetics. References [1] Moser LE. Post-harvest physiology changes in forage plants. In: Moore KJ, Peterson MA, editors. Post-harvest physiology and preservation of forages. Madison, WI: ASA, CSSA; 1995. p. 1-20. CSSA Special Publication 22. [2] Coblentz WK, Fritz JO, Bolsen KK, Cochran RC. Quality changes in alfalfa hay during storage in bales. J Dairy Sci 1996;79:873-85. [3] Coblentz WK, Turner JE, Scarbrough DA, Lesmeister KE, Johnson ZB, Kellogg DW, et al. Storage characteristics and quality changes in bermudagrass hay as affected by moisture content and density of rectangular bales. Crop Sci 2000;40:1375-83. [4] Roberts CA. Microbiology of stored forages. In: Moore KJ, Peterson MA, editors. Post-harvest physiology and preservation of forages. Madison, WI: ASA, CSSA; 1995. p. 21. CSSA Special Publication 22. [5] Rotz CA, Muck RE. Changes in forage quality during harvest and storage. In: Proceeding of the National Conference on Forage Quality, Evaluation, and Utilization, Lincoln, NE. Madison, WI: ASA, CSSA, SSSA; 1994. p. 828-68. [6] Scudamore KA, Livesey CT. Occurrence and significance of mycotoxins in forage crops and silage: a review. J Food Sci Food Agric 1998;77:1-17. [7] Collins M, Paulson WH, Finner MF, Jorgensen NA, Keuler CR. Moisture and storage effects on dry matter and quality losses of alfalfa in round bales. Trans ASAE 1987;30:913-7. [8] Smith TK, Girish CK. The effects of feed born mycotoxins on equine performance and metabolism. In: Mycotoxins in Farm Animals. Kerala, India: Transworld Research Network; 2008. p. 48-70. [9] Muhonen S, Julliand V, Lindberg JE, Bertilsson J, Jansson A. Effects on the equine colon ecosystem of grass silage and haylage diets after an abrupt change from hay. J Anim Sci 2009;87:2291-8. [10] AOAC. Official methods of analysis. 17th ed. Arlington, VA: Association of Official Analytical Chemists; 2000. [11] Pagan JD. Measuring the digestible energy content of horse feeds. In: Advances in equine nutrition. Nottingham, UK: Nottingham University Press; 1998. p. 71-6. [12] EPA. Method 3050B. 1996. Available at: http://www.caslab.com/ EPA-Method-3050B/. [13] Montgomery MJ, Tineo A, Bledsoe BL, Baxter HD. Effect of moisture content at baling on nutritive value of alfalfa orchardgrass hay in conventional and large round bales. J Dairy Sci 1986;69:1847-53. [14] Goering HK, Gordon CH, Hemken RW, Waldo DR, Van Soest PJ, Smith LW. Analytical estimates of nitrogen digestibility in heat damaged forages. J Dairy Sci 1972;55:1275-80. [15] Turner JE, Coblentz WK, Scarbrough DA, Coffey KP, Kellogg DW, McBeth LJ, et al. Changes in nutritive value of bermudagrass hay during storage. Agron J 2002;94:109-17. [16] McBeth LJ, Coffey KP, Coblentz WK, Hellwig DH, Turner JE, Scarbrough DA. Impact of heating-degree-day accumulation during storage of bermudagrass hay on in situ degradation kinetics from steers. Anim Feed Sci Technol 2003;108:147-58. [17] Coblentz WK, Hoffman PC. Effects of bale moisture and bale diameter on spontaneous heating, dry matter recovery, in-vitro true digestibility, and in-situ disappearance kinetics of alfalfaorchardgrass hays. J Dairy Sci 2009;92:2853-74. [18] Roberts CA, Moore KJ, Graffis DW, Kirby HW, Walgenbach RP. Chitin as an estimate of mold in hay. Crop Sci 1987;27:783-5. [19] Adams RS, Kephart KB, Ishler VA, Hutchinson LJ, Roth GW. Mold and mycotoxin problems in livestock feeding. University Park, PA: The Pennsylvania State University, College of Agricultural Sciences and Cooperative Extension Publication; 1993. p. 16. DAS 93-21.
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